Combustion Synthesis and Characterization of Ultra-High-Temperature NbB2–HfB2 Solid Solutions

This paper presents an in-depth study on the combustion synthesis, solid-solution formation, processing, and characterization of NbB₂–HfB₂ ceramics, aiming to explore their potential applications, particularly in industries requiring high-performance materials. We conducted macrokinetic measurements and fitted regression models to predict combustion temperature and velocity for compositions ranging from 50 to 100% HfB₂. A combined method of ball milling and hot pressing was developed for processing the combustion products into dense ceramics. These methods resulted in samples with relative densities reaching 97%, hardness of up to 34 GPa, and Young’s modulus of up to 530 GPa, with NbB₂–50% HfB₂ solid solution exhibiting the best mechanical properties. The study revealed a linear increase in thermal properties and density with the rise in HfB₂ content. The thermal conductivity of the solid solutions in the Nb–Hf–B system ranged from 34 to 40 W/mK and was found to increase with temperature, making these ceramics suitable for ultra-high-temperature applications. The findings have significant implications for aerospace and high-performance engineering sectors and provide a solid foundation for further investigation of Nb–Hf–B ceramics under real-world operational conditions.